[TASK] Change visibility of TSFE properties and methods

The following properties have changed their
visibility to be protected from public.

* pageAccessFailureHistory
* workspacePreview (not in use anymore)
* ADMCMD_preview_BEUSER_uid (not in use anymore)
* debug (not in use anymore)
* MP_defaults (not in use anymore outside of TSFE)
* loginAllowedInBranch (use checkIfLoginAllowedInBranch())

The following methods have changed their signature to be
protected, as their purpose is to be called from within
TypoScriptFrontendController.

- tempPageCacheContent()
- realPageCacheContent()
- setPageCacheContent()
- clearPageCacheContent_pidList()
- setSysLastChanged()
- contentStrReplace()

Resolves: #86047
Releases: master
Change-Id: I98f54f4a75023b963b69c12457b73e5117469497
Reviewed-on: https://review.typo3.org/58083


Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>